Devices and methods for fistula formulation

ABSTRACT

Described here are devices and methods for forming a fistula between two vessels. In some instances, the fistula may be formed between a proximal ulnar artery and a deep ulnar vein. The fistula may be formed using an electrode, and may be formed with a first catheter placed in a first blood vessel and a second catheter placed in a second blood vessel. In some instances, access to the proximal ulnar artery may be achieved through a brachial artery, and access to the deep ulnar vein may be achieved through a brachial vein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 15/344,332, filed on Nov. 4, 2016, which is a continuation ofU.S. Non-Provisional application Ser. No. 14/052,477, filed on Oct. 11,2013, which claims priority to U.S. Provisional Application Ser. No.61/712,704, filed Oct. 11, 2012 and entitled “DEVICES AND METHODS FORFISTULA FORMULATION,” and to U.S. Provisional Application Ser. No.61/785,548, filed on Mar. 14, 2013 and titled “DEVICES AND METHODS FORFISTULA FORMULATION,” the contents of which are hereby incorporated byreference in their entirety.

FIELD

The current invention relates to methods for forming a fistula betweentwo blood vessels.

BACKGROUND

A fistula is generally a passageway formed between two internal organs.Forming a fistula between two blood vessels can have one or morebeneficial functions. For example, the formation of a fistula between anartery and a vein may provide access to the vasculature for hemodialysispatients. Specifically, forming a fistula between an artery and a veinallows blood to flow quickly between the vessels while bypassing thecapillaries. Needles, catheters, or other cannulas may then be insertedinto the blood vessels near the fistula to draw blood from thecirculatory system, pass it through a dialysis machine, and return it tothe body. The quickened flow provided by the fistula may provide foreffective hemodialysis. Generally, fistula formation requires thesurgical dissection of a target vein, transecting and moving the veinfor surgical anastomosis to the artery. These fistulas typically have aprimary failure rate (failure before the patient receives dialysis) ofabout 30-60%, and take between 5 and 12 months before the fistula isusable for dialysis. It may be useful to find improved ways to form afistula between two blood vessels.

BRIEF SUMMARY

In some variations, the methods described here comprise forming a firstfistula between a proximal ulnar artery and a first deep ulnar vein. Insome variations, the methods may further comprise endovascularlyadvancing a distal portion of a first catheter into the first deep ulnarvein. In some of these variations, the first catheter comprises afistula-forming element, and forming the first fistula between theproximal ulnar artery and the first deep ulnar vein comprises formingthe first fistula using the fistula-forming element. The fistula-formingelement may be, for example, an electrode. In some of these variations,the methods further comprise moving the electrode away from the firstcatheter against a vessel wall of the deep ulnar vein, and whereinforming the first fistula between the proximal ulnar artery and thefirst deep ulnar vein comprises ablating the vessel wall of the deepulnar vein and a vessel wall of the ulnar artery.

In some variations, the methods described here may further compriseadvancing a distal portion of a second catheter into the ulnar artery.In some of these variations, the first and second catheters may eachcomprise one or more magnets and the method may further comprisealigning the first and second catheters using the one or more magnets ofeach of the first and second catheters. In some variations, the secondcatheter may comprise a fistula-forming element, and forming the firstfistula between the proximal ulnar artery and the first deep ulnar veincomprises forming the first fistula using the fistula-forming element.The fistula-forming element may be, for example, an electrode. In someof these variations, the method may further comprise moving theelectrode away from the second catheter against a vessel wall of theproximal ulnar artery, and forming the first fistula between theproximal ulnar artery and the first deep ulnar vein may compriseablating the vessel wall of the proximal ulnar artery and a vessel wallof the first deep ulnar vein. In some variations, endovascularlyadvancing the distal portion of the second catheter into the proximalulnar artery comprises endovascularly advancing the distal portion ofthe second catheter into the proximal ulnar artery from a brachialartery. In some of these variations, the method may further comprisecreating an access site in the brachial artery and advancing the secondcatheter into the brachial artery through the access site.

In some variations, endovascularly advancing the distal portion of thefirst catheter into the first deep ulnar vein comprises endovascularlyadvancing the distal portion of the first catheter into the first deepulnar vein from a median cubital vein. In some variations, the methodmay further comprise forming an access site in a basilic vein,introducing the distal portion of the first catheter into the basilicvein through the access site, and advancing the distal portion of thefirst catheter into the median cubital vein through the basilic vein.

In some variations, endovascularly advancing the distal portion of thefirst catheter into the first deep ulnar vein comprises endovascularlyadvancing the distal portion of the first catheter into the first deepulnar vein from a median cephalic vein. In some variations, the methodmay further comprise forming an access site in a cephalic vein,introducing the distal portion of the first catheter into the cephalicvein through the access site, and advancing the distal portion of thefirst catheter into the median cephalic vein through the cephalic vein.In some variations, endovascularly advancing the distal portion of thefirst catheter into the first deep ulnar vein comprises endovascularlyadvancing the distal portion of the first catheter into the first deepulnar vein from a first brachial vein. In some variations, the methodmay further comprise forming an access site in the first brachial vein,introducing the distal portion of the first catheter into the firstbrachial vein through the access site.

In some variations, the methods described here may comprise injecting aradiopaque die into the proximal ulnar artery. Additionally oralternatively, the methods may comprise forming a second fistula betweenthe proximal ulnar artery and a second deep ulnar vein. Additionally oralternatively, the methods may further comprise cannulating the cephalicvein and/or the basilic vein to provide dialysis access.

In other variations, the methods described here may compriseendovascularly advancing a distal portion of a first catheter through aportion of a basilic vein, a median cubital vein, and into a first deepulnar vein, endovascularly advancing a distal portion of a secondcatheter through a portion of a brachial artery and into a ulnar artery,and forming a fistula between the first deep ulnar vein and the ulnarartery. In still variations, the methods described here may compriseendovascularly advancing a distal portion of a first catheter through aportion of a cephalic vein, a median cephalic vein, and into a firstdeep ulnar vein, endovascularly advancing a distal portion of a secondcatheter through a portion of a brachial artery and into a ulnar artery,and forming a fistula between the first deep ulnar vein and the ulnarartery. In yet other variations, the methods described here may compriseendovascularly advancing a distal portion of a first catheter through aportion of a first brachial vein and into a first deep ulnar vein,endovascularly advancing a distal portion of a second catheter through aportion of a brachial artery and into a ulnar artery, and forming afistula between the first deep ulnar vein and the ulnar artery.

BRIEF DESCRIPTION

FIG. 1 is an illustrative depiction of the vascular anatomy of the arm.

FIG. 2 depicts a variation of a catheter system suitable for use withthe methods described here.

FIGS. 3A-3C depict an illustrative method as described here.

FIGS. 4A-4C depict a variation of a device described here for forming afistula.

DETAILED DESCRIPTION

Generally described here are methods for forming one or more fistulasbetween blood vessels of the arm. The methods described here compriseforming a fistula between an ulnar artery and a deep ulnar vein, as willbe described in detail below. The fistula may be formed using one ormore catheters, which may be advanced endovascularly into an ulnarartery and/or a deep ulnar vein. In some variations a first catheter maybe advanced into the ulnar artery, and a second catheter may be placedinto a deep ulnar vein, and the first and second catheters may form afistula therebetween. Access to the vascular sites may be achieved in anumber of ways, such as will be described in more detail below.Accordingly, it may be helpful to briefly describe the anatomy of thevasculature of the arm.

FIG. 1 shows a simplified depiction of the typical vascular anatomy ofthe arm around the elbow. Specifically, FIG. 1 shows an anterior view ofthe right arm as would be seen with the palm facing upward. As shownthere, the brachial artery (100) extends superficially and distally fromthe upper arm and sinks deeply into the arm near the elbow joint, wherethe brachial artery (100) branches into the radial artery (102) and theulnar artery (104). The upper portion of the ulnar artery (104) isdeeply seated within the arm beneath the superficial flexor muscles (notshown), and leads down the ulnar side of the forearm to the wrist. Theanterior ulnar recurrent artery (106) and the posterior ulnar recurrentartery (108) branch off of the ulnar artery (104) just below the elbowjoint, and these arteries supply blood to the joint and surroundingmuscles. Further down the arm (typically just below the radialtuberosity of the radius bone (not shown)), the interosseous artery(109) branches off from the ulnar artery (104) and eventually feeds intothe posterior and anterior interosseous arteries.

Also shown in FIG. 1 are the cephalic vein and the basilic vein. Thecephalic vein runs along the outer border of the bicep muscle (notshown) continues down into the forearm (the cephalic vein of the upperarm is labeled in FIG. 1 as cephalic vein (110), while the cephalic veinof the lower arm is labeled as cephalic vein (114)). The median cephalicvein (116) joins the cephalic vein (110)/(114) near the elbow joint. Thebasilic vein runs along the inner side of the bicep muscle and continuesinto the forearm (the basilic vein of the upper arm is labeled asbasilic vein (112), while the basilic vein of the lower arm is labeledas basilic vein (120)). The median cubital vein (118) (in some instancesreferred to as the median basilic vein) joins the basilic vein(112)/(120) and the common ulnar vein (120) (in some instances, thisvein segment is also referred to as the basilic vein of the forearm orforearm basilica vein). The median cubital vein (118) and the mediancephalic vein (116) are formed at the branching of the medianantebrachial vein (122) (also known as the median vein). Near thebranching of the median vein (122) into the median cubital vein (118)and the medial cephalic vein (116), a perforating branch (124) connectsthese vessels with the deep veins of the arm through the antebrachialfascia (not shown). As shown in FIG. 1, perforating branch (124)communicates with a first deep ulnar vein (126) and a second deep ulnarvein (128). These deep ulnar veins may run substantially parallel oneither side of the ulnar artery (104) between the brachial artery (100)and the interosseous artery (109), and may branch away from ulnar artery(104) distal to the interosseous artery (109). Between the brachialartery (100) and the interosseous artery (109), the deep ulnar veins aretypically located in close proximity to the ulnar artery, and usuallyless than 2 mm separate the ulnar artery from the deep ulnar veins.Along the length of the deep ulnar veins, transverse branches (notshown) may occasionally connect the deep ulnar veins. Also shown in FIG.1 are first (130) and second (132) brachial veins. The brachial veinsgenerally run along the brachial artery (100), and the deep ulnar veinsfeed into the brachial veins near the elbow joint. Additionally, a pairof radial veins ((144) and (146)) may run along the radial artery, andmay feed into one or both of the brachial veins. Also shown in FIG. 1are first (140) and second (142) interosseous veins, which may branchoff from the first (126) and second (128) deep ulnar veins respectively,and which may run substantially parallel to the interosseous artery(109).

As mentioned above, the methods described here comprise forming afistula between an ulnar artery and a deep ulnar vein. Preferably, thefistula is formed at a site in the proximal ulnar artery. As usedherein, the term “proximal ulnar artery” means the ulnar artery betweenthe brachial artery and branch of the interosseous artery. In somevariations, the fistula may be formed between an ulnar artery and a deepulnar vein at a location within about 6 cm from the branch between thebrachial artery and the ulnar artery. In some of these variations, thefistula may be formed at a location less than about 4 cm from the branchbetween the brachial artery and the ulnar artery. Due to their deepanatomic location, the deep ulnar veins are difficult to accesssurgically, and thus are not desirable target sites for conventionalsurgical fistula-forming techniques. The deep anatomic location of thedeep ulnar veins, however, means that these veins are usually undamaged(e.g., by needle sticks or other trauma), which may optimize fistulalongevity. Additionally, because the deep ulnar veins feed into both thecephalic and basilic venous systems, forming a fistula between the ulnarartery and a deep ulnar vein may provide multiple upper-arm cannulationoptions for dialysis patients. As both of the deep ulnar veins feed intothe cephalic and basilic venous systems, either deep ulnar veins may beselected, and in some instances each of the deep ulnar veins may beutilized to form different fistulas.

Generally, the methods described here comprise endovascularly advancinga distal portion of a first catheter into an ulnar artery,endovascularly advancing a distal portion of a second catheter into afirst deep ulnar vein, and forming a fistula between the ulnar arteryand the first deep ulnar vein. As mentioned above, the fistula ispreferably formed between a proximal ulnar artery and a first deep ulnarvein, and thus the methods may comprise endovascularly advancing adistal portion of a first catheter into a proximal ulnar artery,endovascularly advancing a distal portion of a second catheter into afirst deep ulnar vein, and forming a fistula between the proximal ulnarartery and the first deep ulnar vein. When catheters are endovascularlyadvanced into an ulnar artery and/or a deep ulnar vein, access to thesevessels may be achieved in any suitable manner, as will be described inmore detail below. The first and second catheters may be aligned toposition one or more fistula-forming elements (e.g., one or moreelectrodes, mechanical cutting elements, chemical mechanisms,cryogenic-cautery devices, laser ablation devices, combinations thereof,and the like, as will be descried in more detail below) relative to thedesired fistula site. One or both of the first and second catheters maybe advanced or retracted within their respective blood vessels toaxially position the one or more fistula-forming elements relative tothe fistula-formation site. One or both of the first and secondcatheters may be rotated to rotationally position the one or morefistula-forming elements relative to the fistula-formation site (e.g.,to direct a fistula-forming element in the ulnar artery toward a deepulnar vein, to direct a fistula-forming element in a deep ulnar veintoward the ulnar artery, to direct a fistula-forming element in theulnar artery toward a fistula-forming element in a deep ulnar vein,etc.). The methods described here may comprise using one or moremagnets, markers, and/or other alignment elements to assist inpositioning the first and/or second catheters, as will be described inmore detail below. Once the one or more fistula-forming elements arepositioned relative to the fistula-formation site, the fistula-formingelements may be actuated to cut, ablate, or otherwise remove tissuebetween the ulnar artery and the deep ulnar vein to form a fistulatherebetween.

Following activation of the fistula-forming element, one or more stepsmay be conducted to assess the condition of the fistula. For example, insome variations a radiopaque dye (or other suitable contrast media) maybe introduced into the ulnar artery to confirm blood flow into the deepulnar vein from the ulnar artery following activation of thefistula-forming element. In some of these variations, the first and/orsecond catheters may be removed from their respective vessels prior tointroduction of the radiopaque dye into the ulnar artery. In othervariations, the radiopaque dye may be introduced into the ulnar arterythrough the first catheter. In some variations, formation of the fistulamay act to release one or more radiopaque agents from the first and/orsecond catheters. For example, in some variations, a first catheteradvanced into an ulnar artery may comprise a fistula-forming element,and a second catheter advanced into a deep ulnar vein may comprise aballoon housing a radiopaque agent therein. The first and secondcatheters may be aligned such that activation may form a fistula betweenthe ulnar artery and deep ulnar vein and also punctures the balloon torelease the radiopaque agent.

The methods described here may further comprise forming a second fistulabetween the ulnar artery and a second deep ulnar vein. For example, if auser or physician determines that there is insufficient flow between theulnar artery and a first deep ulnar vein, a second fistula may be formedbetween the ulnar artery and a second deep ulnar vein. The secondfistula may be formed during the same procedure, or may be formed duringa subsequent procedure. The second fistula may be formed using any ofthe methods described hereinthroughout.

Because the deep ulnar veins feed into both the cephalic and basilicsystems, a patient having a fistula between an ulnar artery and a deepulnar vein be cannulated using a blood vessel from either system toprovide dialysis access. In some variations, the methods described heremay comprise allowing a fistula formed between an ulnar artery and adeep ulnar vein to mature (this may take as long as six or more months),and cannulating either the cephalic and basilic systems to providevascular access. The methods may further comprise assessing the flowthrough a vein of the cephalic or basilic system, selecting a veinhaving a flow rate suitable for dialysis access (which is some instancesmay be approximately 600 ml/min), and cannulating that vein to providevascular access. In some variations, this may comprise cannulating aportion of the median cubital vein. In some variations, this maycomprise cannulating a portion of the cephalic vein. In othervariations, this may comprise cannulating a portion of the basilic vein.In some variations, both the cephalic and basilic veins may becannulated, as will be described in more detail below. In variationswhere the cephalic vein is cannulated, the methods may further compriseligating or coil embolizing the median cubital vein to prevent or reduceflow from the fistula into the basilic vein. Conversely, in variationswhere the basilic vein is cannulated, the methods may comprise ligatingor coil embolizing the median cephalic vein to reduce flow from thefistula into the cephalic vein.

In some variations, the methods may further comprise ligating or coilembolizing at least one brachial vein. In these variations, one or bothof the brachial veins may be ligated or coil embolized. Restricting flowthrough the brachial veins may divert flow to cephalic and/or basilicsystems, which may improve flow therethrough. In these variations, thebrachial vein or veins may be closed off during the same procedure inwhich the fistula is formed, or may be closed off during a laterprocedure (e.g., between about four weeks and about eight weeksfollowing formation of the fistula). In some variations, a firstbrachial vein may be closed off during the fistula-forming procedure,while a second brachial vein may be closed during a subsequentprocedure.

It should be appreciated that the methods described here may be used toform a fistula between the ulnar artery and deep ulnar vein that may notrequire a stent or other connecting structure to maintain patency of thefistula. In some variations, however, the methods described here mayfurther comprise placing a stent, tube, or other structure between theulnar artery and deep ulnar vein. Additional, while the methodsdescribed immediately above may comprise advancing catheters into boththe ulnar artery and a deep ulnar vein, respectively, it should beappreciated that in some variations a fistula may be formed using only afirst catheter placed in a deep ulnar vein, or may be formed using onlya first catheter placed in the ulnar artery. When a first catheter isplaced in the ulnar artery and a second catheter is placed in a deepulnar vein, either catheter or both catheters may comprise one or morefistula-forming elements. When a first catheter placed in the ulnarartery comprises a fistula-forming element, that fistula-forming elementmay form the fistula directionally from the ulnar artery into the deepulnar vein. When a second catheter placed in the ulnar artery comprisesa fistula-forming element, that fistula-forming element may form thefistula directionally from the deep ulnar vein into the ulnar artery.When both first and second catheters comprise fistula-forming elements,the fistula may be formed directionally from the deep ulnar vein intothe ulnar artery, directionally from the ulnar artery into a deep ulnarvein, or may be formed simultaneously from both the ulnar artery and adeep ulnar vein.

Any suitable catheter or catheters may be used to form the fistulasusing the methods described here. The methods described here may use oneor more of the devices as described in U.S. patent application Ser. No.13/298,169, filed on Nov. 16, 2011 and titled “DEVICES AND METHODS FORFORMING A FISTULA,” which is hereby incorporated by reference in itsentirety. In some variations, a fistula may be formed using a firstcatheter placed in the ulnar artery and a second catheter placed in thedeep ulnar vein. FIG. 2 show one variation of a catheter system (200)that may be used to form a fistula between the ulnar artery and a deepulnar vein. As shown there, system (200) may comprise a first catheter(202) and a second catheter (203). The first catheter (202) may comprisea catheter body (204) and an electrode (206) which may be advanced outof an opening (205) in the catheter body (204). Current may be passedthrough the electrode (206) to ablate or otherwise remove tissuecontacted by the electrode (206). In some variations, the first catheter(202) may comprise an insulating housing (208) (e.g., a ceramic housingor the like) within the catheter body, which may help protect othercomponents of the first catheter (202) from heat that may be generatedby the electrode (206) during tissue removal. The electrode (206) may beselectively moved from a position in which the electrode (206) isretained or otherwise held in the catheter body (204) to a position inwhich the electrode (206) extends away from the catheter body (204)(such as shown in FIG. 2), and electrode (206) may also be selectivelymoved back to a retracted/low-profile position (either the same or adifferent position as the previous retracted position) followingablation of tissue. In some variations, the electrode (206) may bebiased toward an extended position when not otherwise restrained by thecatheter body (204). While a fistula-forming element comprising anelectrode (206) is shown in FIG. 2, it should be appreciated that themethods described here may utilize a catheter comprising any suitablefistula-forming element (e.g., one or more electrodes/electrocauterymechanisms, cone or more mechanical cutting mechanisms such as blades,lances, needles, or the like, one or more chemical devices,cryogenic-cautery devices, laser ablation devices, combinations thereofand the like), such as those described in more detail in U.S. patentapplication Ser. No. 13/298,169, which was previously incorporated byreference in its entirety, and may be operated in any manner asdescribed therein.

While shown in FIG. 2 as having both first (202) and second (203)catheters, system (200) need not comprise two catheters. For example, invariations of the methods described here in which a fistula is formedusing a catheter placed only in the ulnar artery or only in a deep ulnarvein, the system (200) may comprise only a first catheter (202). Invariations that do have a second catheter (203), the catheter (203) mayhave any suitable elements or combination of elements. For example, thesecond catheter (203) may comprise a catheter body (208) having a recess(210) extending therein. The recess (210) may be coated by an insulatingmaterial (not shown), which may act as a backstop to receive and contactthe electrode (206) of the first catheter without damaging one or morecomponents of the first catheter (202). Additionally or alternatively,the second catheter (203) may comprise one or more fistula-formingelements, which may be the same as or different from the fistula formingelement or elements of the first catheter (202).

The methods described here may utilize one or more catheters comprisingone or more alignment elements, which may help to position catheterswithin the vasculature. For example, in some variations a method maycomprise using one or more alignment elements to help bring two or morecatheters (and with them, associated blood vessels) in closerapproximation. Additionally or alternatively, a method may compriseusing one or more alignment elements to position one or more cathetersin a specific rotational configuration relative to the blood vesselsand/or the other catheters. Additionally or alternatively, a method maycomprise using one or more alignment elements to position one or morecatheters axially within a blood vessel or blood vessels. For example,one or more alignment elements may be configured to position afistula-forming element of a catheter relative to the ulnar artery and adeep ulnar vein such that activation of the fistula-forming elementdirects fistula formation between the two vessels.

In some variations, a catheter may comprise one or more magneticalignment components. Examples of magnet arrangements for use with thecatheters described here may be found in in U.S. patent application Ser.No. 13/298,169, which was previously incorporated by reference in itsentirety. These magnetic alignment components may be attracted to one ormore additional elements (e.g., one or more portions of a secondcatheter, one or more magnets or other components placed externally fromthe body) to help position or align the catheter within a vessel. Forexample, one or more magnets placed outside of the body may interactwith the magnetic alignment components of a catheter to help facilitateadvancement of the catheter through the vasculature. Additionally oralternatively, one or more magnetic alignment elements of a firstcatheter may interact with one or more magnetic alignment elements of asecond catheter to attract the first and second catheters toward eachother, and/or to bias the first and second catheters toward a specificrotational and/or axial alignment.

For example, in the variation of system (200) shown in FIG. 2, each offirst (202) and second (203) catheters may comprise a plurality ofmagnetic alignment elements (212). These magnetic alignment elements(212) may be configured to bias the axial positioning of the first (202)and second (203) catheters such that the opening (205) of the firstcatheter (202) axially aligns with the recess (210) of the secondcatheter (203). The magnetic alignment elements (212) may also beconfigured to bias the rotational positioning of the first (202) andsecond (203) catheters such that the opening (205) of the first catheter(202) faces toward the recess (210) of the second catheter (203).Accordingly, the magnetic alignment elements (212) may be used to helpposition the first (202) and second (203) catheters within respectiveblood vessels such that the electrode (206) may be extended from opening(205) toward recess (210) of the second catheter (203) during fistulaformation.

Additionally or alternatively, in some variations, the catheter maycomprise one or more shape-changing elements for approximating two ormore blood vessels. In these variations, the shape-changing element mayhave a first configuration during advancement of the catheter throughthe vasculature. Once the catheter reaches a target location, theshape-changing element may be altered to a second configuration, whichmay alter the overall shape of the catheter. As the catheter changesshape, the catheter may move or reconfigure one or more portions of theblood vessel, which may help bring that portion or portions of the bloodvessel in closer approximation to one or more portions of a second bloodvessel. Examples of shape-changing elements for use with the cathetersdescribed here may be found in in U.S. patent application Ser. No.13/298,169, which was previously incorporated by reference in itsentirety.

Additionally or alternatively, the methods may comprise visualizing oneor more markers from one or more catheters during advancement andpositioning thereof. In some variations, the marker may be directlyvisualized. In other variations, the marker may be indirectly visualized(e.g., via ultrasound, fluoroscopy and/or X-ray visualization). Markersmay be located anywhere relative to the catheter, e.g., one or moresurfaces of the catheter, inside of the catheter. In some variations,one or more portions of the catheter may be made from an echogenic orradiographic material. A marker may be attached to the catheter by anysuitable method, for example, by mechanical attachment (e.g., embeddedin a portion of the catheter, circumferential circumscription, or thelike), adhesive bonding, welding, soldering, combinations thereof or thelike. For example, in the variation of system (200) shown above in FIG.2, each of the first (202) and second (203) catheters may comprise oneor more markers (214). These markers (214) may be visualized duringadvancement and/or position of the first (202) and second (203)catheters to confirm that the catheters are properly positioned withinthe blood vessels. For example, in variations where a method comprisesaxially aligning the opening (205) of the first catheter (202) relativeto the recess (210) of the second catheter (203) and/or rotationallyaligning the opening (205) of the first catheter (202) relative to therecess (210) of the second catheter (203), the method may furthercomprise visualizing one or more markers (214) of the first (202) and/orsecond (203) catheters to confirm this positioning.

In some variations, one or more of the catheters may comprise one ormore balloons or other expandable structures. These expandablestructures may serve one or more functions. In some instances, anexpandable structure may help appose an electrode surface (or otherfistula-forming element) against one or more vessel walls. Thisapposition may help temporarily flatten or otherwise relocate tissue,and may act to displace blood from the area. Additionally, duringfistula formation, the expandable member may continue to urge thefistula forming element against tissue as it is removed from the vesselwall. In some variations, the expandable structure may be configured tohelp provide apposition between the catheter and a vessel wall, whilestill allowing for blood flow through the blood vessel. In someinstances, one or more expandable structures may help modify orotherwise alter the size or shape of a fistula. In still otherinstances, the expandable structures may be used to dilate, contract, orotherwise displace a portion of one or more blood vessels. In some ofthese variations, this displacement may help bring a portion of theblood vessel closer to a skin surface.

FIGS. 3A-3C depict an illustrative method by which the catheter system(200) of FIG. 2 may be used to form a fistula between a first deep ulnarvein and an ulnar artery. The labeling of FIGS. 1 and 2 will be used forcommon elements and anatomical locations. As shown in FIG. 3A, themethod may comprise endovascularly advancing a distal portion of a firstcatheter (202) into an ulnar artery (104). In the method shown in FIG.3A, the first catheter (202) may be advanced into the ulnar artery (104)from the brachial artery (100). In some variations, the method maycomprise creating an access site (not shown) in the brachial artery(100), and advancing the first catheter (202) into the brachial artery(100) through the access site. It should be appreciated, however, thatthe first catheter (202) may be advanced into the ulnar artery in anysuitable manner, as described in more detail below.

As shown in FIG. 3B, the method may further comprise endovascularlyadvancing a second catheter (203) into a first deep ulnar vein (126) (itshould be appreciated that the second catheter (203) may be advancedinto either of the deep ulnar veins (126) or (128)). In the method shownin FIG. 3B, the second catheter (203) may be advanced into the firstdeep ulnar vein (126) from the perforating branch (124), which may beaccessed by advancing the second catheter (203) through the basilic vein(112) and the median cubital vein (118). In some variations, the methodmay comprise creating an access site (not shown) in the basilic vein(112), and advancing the second catheter (203) into the basilic vein(112) through the access site. It should be appreciated, however, thatthe second catheter (203) may be advanced into the deep ulnar vein (126)in any suitable manner, as described in more detail below. While thefirst catheter (202) is shown in FIG. 3A as being advanced into ulnarartery (104) prior to advancement of the second catheter (203) into thedeep ulnar vein (126), it should be appreciated that the first (202) andsecond (203) catheters may be advanced in any order.

Once the distal ends of the first (202) and second (203) catheters havebeen advanced into the ulnar artery (104) and deep ulnar vein (126), thefirst (202) and second (203) catheters may be axially positionedrelative to one another to align the opening (205) of the first (202)catheter with the recess (210) of the second catheter (203), as shown inFIG. 3C. Additionally, the first (202) and second (203) catheters may beaxially positioned relative to the ulnar artery (104) and deep ulnarvein (126) respectively such that the opening (205) of the firstcatheter (202) and recess (210) of the second catheter (203) are axiallyaligned with the desired fistula formation site. In some instances, whenthe opening (205) of the first catheter (202) and recess (210) of thesecond catheter (203) are axially aligned with the desired fistulaformation site (e.g., in a ulnar artery and a deep ulnar vein), thedistal tips of the first and second catheters may extend into the ulnarartery (104) and deep ulnar vein (126) distally of the branching of theinterosseous artery (109) and the interosseous veins (e.g. the firstinterosseous vein (140)), such as shown in FIG. 3B. Alternatively, whenthe opening (205) of the first catheter (202) and recess (210) of thesecond catheter (203) are axially aligned as discussed above, a distaltip of the first catheter (202) may extend into the interosseous artery(109) and/or the distal tip of the second catheter (203) may extend intoan interosseous vein (e.g., first interosseous vein (140)).

Additionally, the first (202) and second (203) catheters may berotationally aligned such that opening (205) may face the recess (210)of the second catheter (203). As mentioned above, in some variations,the methods may comprise using one or more magnetic alignment elements(212) help achieve the axial or rotational positioning of the first(202) and second (203) catheters. Additionally or alternatively, thepositioning of the first (202) and second (203) catheters may beconfirmed by visualizing magnets (214) of the first and/or secondcatheters.

Once the first (202) and second (203) catheters are positioned relativeto each other and their respective vessels, the electrode (206) may beadvanced out of the opening (205) of the first catheter (202) to pressthe electrode (206) against a vessel wall of the ulnar artery (104).Energy may be delivered to the electrode (206) to cut tissue, which mayadvance the electrode (206) from the ulnar artery (104), through thewall of the deep ulnar vein (126), and into the deep ulnar vein (126).In some variations, the first catheter (202) comprising the electrode(206) may be placed in the deep ulnar vein (126) and the second catheter(203) may be placed in the ulnar artery (104), such that the electrode(206) may be advanced from the deep ulnar vein (126) into the ulnarartery (104). Once the fistula has been has been formed between theulnar artery (104) and the deep ulnar vein (126), one or more contrastagents may be passed through the fistula and/or a second fistula may beformed, such as described in more detail above.

It should be appreciated that in some or all of the methods describedhere, one or more portions of the patient may be immobilized during someall of the steps of the method. For example, when a fistula is formedbetween two vessels in an arm, one or more portions of the arm (e.g., awrist, an elbow, or the like) may be immobilized. In some of thesevariations, a wrist of the patient may be immobilized. When a wrist isimmobilized, the wrist may be immobilized prior to creating access toone or more blood vessels. In some of these variations, the wrist mayremain immobilized until after formation of the fistula. It should beappreciated that when a portion of the arm is immobilized, the arm maybe temporarily released to reposition the arm, if needed.

FIGS. 4A and 4B depict perspective views and 4C depicts across-sectional side view of a device (400) which may be used to form afistula. While the device (400) may be used to form a fistula betweentwo or more vessels as described above, the device (400) may be used toform a fistula between any two vessels, such as described here and inU.S. patent application Ser. No. 13/298,169, which was previouslyincorporated by reference in its entirety. As shown in FIG. 4A, thedevice (400) may comprise a first arm (402), a second arm (404), ahandle (406), and a fistula-forming element (408). Generally, the firstarm (402) and the second arm (404) may be formed from one or more rigidmaterials (e.g., one or more metals such as stainless steel, one or moreplastics, combinations thereof and the like), such that when each arm ispositioned in a respective blood vessel, the vessel may substantiallyconform to the shape of the arm.

In the variation shown in FIGS. 4A-4C, the handle (406) may comprise aconnection portion (414) and a grip portion (416). The grip portion(416) may be sized and configured such that it may be held by a user,and may have any suitable dimensions. For example, in some variationsthe grip portion (416) may have any suitable length (e.g., between about8 cm and about 25 cm, between about 12 cm and about 20 cm, or the like)and any suitable diameter (e.g., between about 3 cm and about 12 cm,between about 5 cm and about 8 cm, and the like). The connection portion(414) (which may be connected to a distal end of the grip portion (416))is generally configured to position the first (402) and second (404)arms relative to each other. As shown there, the first arm (402) may befixedly connected to the connection portion (414) and the second arm(404) may be adjustably connected to the connection portion (414).Specifically, a proximal end of the second arm (414) may comprise aconnector (418) having a track (420) (as illustrated in across-sectional side view in FIG. 4C), and a knob (422) may connect theconnector (418) to the connection portion (414). Specifically, the knob(422) may comprise a pin (424) which may extend through the track (420)and into the connection portion (414). The knob (422) may be rotated ina first direction to lock the connector (418) relative to the connectionportion (414), and may be rotated in a second direction to allow theconnector (418) to be adjusted relative to the connection portion (414).

When the connector (418) is adjustable relative to the connectionportion (414), the track (420) may be rotated and/or slid relative tothe pin (424). Rotation of the connector (418) may rotate the second arm(404) relative to the first arm (402), while sliding of the connector(418) may adjust the distance between the second arm (404) and the firstarm (402). Accordingly, the position of the second arm (404) may beadjusted to set a specific relation between the first arm (402) and thesecond arm (404), and the knob (422) may be adjusted to temporarily lockthe position of the second arm (404) relative to the first arm (402).When the first arm (402) and the second arm (404) are placed in firstand second vessels, respectively, the relative positioning between thefirst and second arms may also dictate the relative positioning betweenthe first and second vessels.

The fistula-forming element (408) may be any suitable fistula-formingelement (e.g., a cutting mechanism, an electrode) as described in moredetail above. In the variation shown in FIGS. 4A-4C, the fistula-formingelement may comprise a blade (409) connected to the first arm (402). Theblade (409) may be rotatable between a low-profile configuration inwhich the blade (409) is housed within the first arm (402) (as shown inFIG. 4C) and a cutting configuration in which the blade (409) extendsfrom the first arm (402) (as shown in FIG. 4B). As the blade (409)rotates out of the first arm (402), a cutting edge of the blade (409)may cut tissue. In some variations, the blade (409) may also act as anelectrode to deliver current to tissue. The blade (409) may be rotatedin any suitable manner. In the variation of the device (400) shown inFIGS. 4A-4C, the device (400) may comprise a blade control knob (410).The blade control knob (410) may be connected to a linkage (412), whichin turn may be connected to the blade (409). The linkage (412) may beconfigured such that rotation of the control knob (410) in a firstdirection advances the linkage (412), which in turn rotates the blade(409) from the low-profile configuration to the cutting configuration.Conversely, rotation of the control knob (410) in a second direction mayretract the linkage (412), which in turn may rotate the blade (409) fromthe cutting configuration to the low-profile configuration. While thefistula-forming element (408) is shown in FIG. 4A as being connected tothe first arm (402), it should be appreciated that in some instances thefistula-forming element (408) may be connected to the second arm (404),and in other instances both the first arm (402) and the second arm (404)may comprise a fistula-forming element.

As mentioned above, the device (400) may be used to form a fistula. Inthese variations, the first arm (402) may be introduced into a firstblood vessel and the second arm (404) may be introduced into a secondblood vessel. The position of the second arm (404) relative to thesecond arm (402) may be adjusted to reposition the second blood vesselrelative to the first blood vessel. When the blood vessels arepositioned as desired, the second arm (404) may be fixed relative to thefirst arm (402) (e.g., by rotating the knob (422)). With the arms set ina fixed relation, the fistula-forming element (408) may be activated toform a fistula. For example, this may comprise rotating the blade (409)relative to the first arm (402) to cut tissue of the first and secondblood vessels positioned between the first arm (402) and the second arm(404).

Ulnar Artery Access

In variations where a catheter or other tool is advanced endovascularlyinto the ulnar artery, access to the ulnar artery may be achieved in anysuitable manner. In some variations, the catheter may be advanced alongthe brachial artery and into the ulnar artery. In some of these methods,the catheter may be introduced into the vasculature via a brachialaccess site. In some of these methods, the brachial artery may becannulated with a cannula directed distally in the brachial artery. Thecannula may be any suitable size (e.g., about 5 Fr, about 7 Fr, betweenabout 5 Fr and about 7 Fr), and may be introduced into the brachialaccess site in any suitable manner, for example, using Seldingertechnique, a micropuncture set, and/or a cutdown procedure. In othervariations, the catheter may be advanced along the brachial artery froman access site upstream of the brachial artery. For example, thecatheter may introduced into the vasculature via a femoral artery accesssite, and may be advanced to the brachial artery therefrom. In somevariations, the ulnar artery may be accessed directly. In some of thesevariations, an ulnar access site may be formed in the ulnar artery(e.g., at a distal location in the wrist or forearm where the ulnarartery is superficially positioned), and a catheter may be advanced in aretrograde fashion through the ulnar access site. In these variations,the ulnar artery may be cannulated as described above. In still othervariations, a catheter or other tool may be advanced endovascularly intothe ulnar artery through an access site in the radial artery.

The catheter may be advanced into the ulnar artery using one or morevisualization techniques (e.g., via fluoroscopy, ultrasound,combinations thereof, or the like). In some variations, the catheter maybe advanced over or along a guidewire which may be placed at the targetfistula formation site via one or more of the vascular access sitesdescribed immediately above.

Deep Ulnar Vein Access

In variations where a catheter or other tool is advanced endovascularlyinto a deep ulnar vein, access to the deep ulnar vein may be achieved inany suitable manner. In some variations, the catheter is introduced intothe vascular site via an access site. A vascular access site may beformed using a micropuncture set, an access needle (e.g., a 18 or 19gauge access needle), and/or using a surgical cut-down procedure, suchthat a cannula may be placed in the blood vessel. The venous access sitemay be in any suitable blood vessel, such as the basilic vein, thecephalic vein, or a brachial vein.

In some variations, the catheter may be advanced to a deep ulnar veinendovascularly along the median cubital vein. For example in somevariations, the catheter may be advanced along the basilic vein, intothe median cubital vein, and into one of the deep ulnar veins via theperforating branch extending between the median cubital vein and thedeep ulnar veins. In instances where the perforating branch extendsbetween the deep ulnar veins and the median antebrachial vein, thecatheter may be advanced from the median cubital vein into the medianvein, then into one of the deep ulnar veins.

In other variations, the catheter may be advanced to a deep ulnar veinendovascularly along the median cephalic vein. For example, in somevariations, the catheter may be advanced into the vasculature through anaccess site in the cephalic vein, and may be endovascularly advancedfrom the cephalic vein into the median cephalic vein, and into one ofthe deep ulnar veins via a perforating branch (to access the perforatingbranch, it may be necessary to advance the catheter into either themedian cubital vein or the median antebrachial vein).

In still other variations, the catheter may be advanced to a deep ulnarvein endovascularly along a brachial vein. For example, in somevariations, the catheter may be advanced into the vasculature through anaccess site in a brachial vein, and may be endovascularly advanced fromthe brachial vein into one of the deep ulnar veins in a retrogradefashion.

The catheter may be advanced into the deep ulnar vein using one or morevisualization techniques (e.g., via fluoroscopy, ultrasound,combinations thereof, or the like). In some variations, the catheter maybe advanced over or along a guidewire which may be placed at the targetfistula formation site via one or more of the vascular access sitesdescribed immediately above.

Dialysis Access

As mentioned above, one or more veins may be cannulated followingfistula formation to provide dialysis access. Generally, providingdialysis access comprises cannulating one or more blood vessels with afirst needle and a second needle. Generally, one of the needles may bean arterial needle configured to supply blood to a dialysis machine,while the other needle may be a venous needle configured to return bloodto the patient. In some variations, both the first and second needlesmay be placed in the cephalic vein. In other variations, both the firstand second needles may be placed in the basilic vein. In still othervariations, both the first and second needles may be placed in themedian cubital vein. When both the first and second needles are placedin the same vein segment, it may be desirable to place the arterial andvenous needles such that they are at least about 5 cm apart, which mayreduce the likelihood that blood returned to the patient through thevenous needle is taken up by the arterial needle.

In other variations, the first and second needles may be positioned indifferent blood vessels. In some variations, a first needle may beplaced in a basilic vein and a second needle may be placed in a mediancubital vein (e.g., an arterial needle may be placed in the mediancubital vein and a venous needle may be placed in the basilica vein). Inother variations, a first needle may be placed in a cephalic vein and asecond needle may be placed in a median cubital vein (e.g., an arterialneedle may be placed in the median cubital vein and a venous needle maybe placed in the cephalic vein). In still other variations, a firstneedle may be placed in a cephalic vein and second needle may be placedin a basilic vein (e.g., an arterial needle may be placed in the basilicvein and a venous needle may be placed in the cephalic vein). In thesevariations, the needle placed in the cephalic vein may be either thearterial needle or the venous needle. When a first needle and secondneedle are positioned in different blood vessels (e.g., when a firstneedle is placed in the basilic vein and a second needle is placed inthe antecubital vein or the cephalic vein), there may be a reducedlikelihood that blood returned to the body via the venous needle (whichmay be either the first or second needle) may be taken up by thearterial needle.

Example 1

A total of nine patients received a percutaneously-formed fistulabetween a proximal ulnar artery and a deep ulnar vein of an arm of eachpatient. To form the fistula, a first catheter carrying an electrode waspercutaneously positioned in the deep ulnar vein (via brachial veinaccess) and a second catheter was percutaneously positioned in theproximal ulnar artery (via brachial artery access), and the electrodeablated tissue between the deep ulnar vein and the proximal ulnar arteryto remove tissue between the vessels. The arm was immobilized at thewrist during the formation of the fistula. Patient follow-ups occurredat one month, two months, and three months. At the first follow-up, oneor more vessels were coil embolized in some patients at the discretionof the physician.

As shown in Table 1, a fistula was successfully formed in nine of ninepatients. For the nine patients, the average time to dialysis readinesswas 62 days. Dialysis readiness was determined based on successfulinitiation of dialysis or physical determination of a flow rate of atleast 300 ml/min. Nine of the nine patients maintained fistula and veinpatency at three months.

TABLE 1 Results from Example 1 Patient Study (9 patients) ResultsSuccessful fistula formation 100% (9/9) Average time to dialysisreadiness 62 days (n = 9) Fistula/vein patency at three months 100%(9/9)

Example 2

A total of seven patients received a percutaneously-formed fistulabetween a proximal ulnar artery and a deep ulnar vein of an arm of eachpatient. To form the fistula, a first catheter carrying an electrode waspercutaneously positioned in the deep ulnar vein (via cephalic, basilic,or brachial vein access) and a second catheter was percutaneouslypositioned in the proximal ulnar artery (via brachial artery access),and the electrode ablated tissue between the proximal ulnar artery andthe deep ulnar vein to remove tissue between the vessels. The arm wasnot immobilized during the formation of the fistula. Patient follow-upsoccurred at one, two, and three months. During follow-ups, one or morevessels were coil embolized in some patients at the discretion of thephysician. Two patients received balloon angioplasty at three months,and one patient received balloon angioplasty and surgical revision atthree months.

As shown in Table 2, a fistula was successfully formed in six of sevenpatients. Of the six patients with a successfully-formed fistula, eachmaintained fistula and vein patency at three months. One patient waswithdrew from the study after the three-month evaluation. Of theremaining five patients, the average time to dialysis readiness was 108days. Dialysis readiness was determined based on successful initiationof dialysis or physical determination of a flow rate of at least 300ml/min.

TABLE 2 Results from Example 2 Patient Study (7 patients) ResultsSuccessful fistula formation 86% (6/7) Average time to dialysisreadiness 108 days (n = 5) Fistula/vein patency at three monthsfollowing 100% (6/6) successful fistula formation

Example 3

A total of eight patients received a percutaneously-formed fistulabetween a proximal ulnar artery and a deep ulnar vein of an arm of eachpatient. To form the fistula, a first catheter carrying an electrode waspercutaneously positioned in the deep ulnar vein (via brachial veinaccess) and a second catheter was percutaneously positioned in theproximal ulnar artery (via brachial artery access), and the electrodeablated tissue between the proximal ulnar artery and the deep ulnar veinto remove tissue between the vessels. The arm was immobilized at thewrist during the formation of the fistula. The brachial vein was coilembolized during the procedure. Patient follow-ups occurred at one, two,and three months.

As shown in Table 3, a fistula was successfully formed in all eightpatients. One patient died of causes unrelated to the procedure(arrhythmia caused by hyperkalemia) prior to the two-month evaluation. Asecond patient achieved dialysis readiness, but died of causes unrelatedto the procedure (septicemia from diabetic foot ulcer) prior to thethree-month evaluation. Of the six patients that received a three-monthevaluation, five maintained fistula and vein patency at three months.For the six patients that achieved dialysis readiness, the average timeto dialysis readiness was 37 days. Dialysis readiness was determinedbased on successful initiation of dialysis or physical determination ofa flow rate of at least 300 ml/min.

TABLE 3 Results from Example 3 Patient Study (8 patients) ResultsSuccessful fistula formation 100% (8/8) Average time to dialysisreadiness 37 days (n = 6) Fistula/vein patency at three months 83% (5/6)

1.-29. (canceled)
 30. A device for forming a fistula between two vesselscomprising: a handle; a first arm fixedly connected to the handle; and asecond arm adjustably connected to the handle, wherein at least one ofthe first arm and the second arm comprises a fistula forming element.31. The device of claim 30, wherein the fistula forming elementcomprises a rotatable blade.
 32. The device of claim 31, wherein therotatable blade is rotatably connected to a distal portion of the firstarm.
 33. The device of claim 32, wherein the handle comprises a firstcontrol configured to rotate the rotatable blade relative to the firstarm.
 34. The device of claim 30, further comprising an adjustment knob,wherein the adjustment knob is moveable between a first configuration tolock the second arm relative to the first arm and a second configurationto allow adjustment of the second arm relative to the first arm.
 35. Thedevice of claim 30, wherein the first arm is formed from a first rigidmaterial such that placement of the first arm in a first vessel causesthe first vessel to conform to a shape of the first arm.
 36. The deviceof claim 35, wherein the second arm is formed from a second rigidmaterial such that placement of the second arm in a second vessel causesthe second vessel to conform to a shape of the second arm.
 37. A devicefor forming a fistula between two vessels comprising: a handlecomprising: a grip portion; and a connection portion connected to thegrip portion; a first arm connected to the connection portion; and asecond arm connected to the connection portion, wherein the connectionportion is configured to adjustably position the first arm and thesecond arm relative to each other.
 38. The device of claim 37, whereinthe first arm is fixedly connected to the connection portion and thesecond arm is adjustably connected to the connection portion.
 39. Thedevice of claim 38, wherein the second arm is lockable in a positionrelative to the first arm.
 40. The device of claim 37, wherein the firstarm is configured to be inserted into a first vessel and the second armis configured to be positioned into a second vessel, and wherein anadjustment of a position of the second arm relative to the first armwith the connection portion repositions the second vessel relative tothe first vessel.
 41. The device of claim 37, further comprising anadjustment knob, wherein the adjustment knob is moveable between a firstconfiguration to lock the second arm relative to the first arm and asecond configuration to allow adjustment of the second arm relative tothe first arm.
 42. The device of claim 37, wherein the first arm isformed from a first rigid material such that placement of the first armin a first vessel causes the first vessel to conform to a shape of thefirst arm.
 43. The device of claim 42, wherein the second arm is formedfrom a second rigid material such that placement of the second arm in asecond vessel causes the second vessel to conform to a shape of thesecond arm.
 44. A device for forming a fistula between two vesselscomprising: a handle comprising: a grip portion; and a connectionportion connected to the grip portion; a first arm connected to theconnection portion; and a second arm comprising a fistula formingelement, wherein the second arm is connected to the connection portionand the connection portion is configured to adjustably position thefirst arm and the second arm relative to each other.
 45. The device ofclaim 44, wherein the first arm is fixedly connected to the connectionportion and the second arm is adjustably connected to the connectionportion.
 46. The device of claim 45, wherein the second arm is lockablein a position relative to the first arm.
 47. The device of claim 44,wherein the first arm is configured to be inserted into a first vesseland the second arm is configured to be positioned into a second vessel,and wherein an adjustment of a position of the second arm relative tothe first arm with the connection portion repositions the second vesselrelative to the first vessel.
 48. The device of claim 44, wherein thefistula forming element comprises a rotatable blade.
 49. The device ofclaim 48, wherein the rotatable blade is rotatable connected to a distalportion of the first arm.